A video laryngoscope is a relatively new development in the field of anaesthesia.
Traditional DIRECT LARYNGOSCOPY (DL) involves using a blade with a light at the end to obtain a view of the glottis via a direct view from the maxillary teeth to the vocal cords. This allows passage of an endotracheal (ET) tube under direct vision. Direct laryngoscopy involves alignment of the oral, pharyngeal and tracheal axes to produce this view.
RIGID INDIRECT LARYNGOSCOPY (RIL) involves obtaining a view of the glottis without alignment of the oral, pharyngeal and tracheal axes. This view is obtained with prisms, mirrors and fibre-optics in the past and more recently with video cameras (i.e. CMOS or CCD camera).
Although initially used primarily as rescue devices (i.e. when DL has failed) video laryngoscopes are being increasingly used as primary devices as well. Given that the view of the glottis is obtained by a video camera, the image obtained has to be displayed on a monitor for the user to guide the placement of an ET tube. There are two primary monitor types as described in the following.
The first type of monitor is external and does not move relative to the position/angle of the handle and is in a fixed position relative to the user. The advantage is that the monitor is always in the same position relative to the user. The disadvantages are that adjusting the monitor would require abandoning the attempt or a second person available to adjust the monitor and that the monitor is often out of the immediate field of view of the user. The user must look at the mouth of the patient during the attempt to place the VL blade, to advance the VL blade, to suction the airway and to place the ET tube into the mouth. Therefore, having the monitor out of the immediate line of site of the user may cause them to lose situational awareness of the patient during the attempt while the user glances between the monitor and the patient.
To address the deficiencies of the first type of monitor, the second monitor type is a monitor mounted on the handle, typically on a “hinge” that allows the user to vary the angle of the monitor relative to the handle to the user's preference in one to three axes (pitch, roll and/or yaw). Once in position, the monitor will stay in a fixed position relative to the handle until manually re-positioned by the user. The advantage is that the monitor and the patient's mouth is always in the immediate field of view of the user. The disadvantage is that the once the procedure is started adjusting the monitor's position relative to the handle would require using the users right hand (which then can't be used for suction or holding the ET tube) or adjusting the user's head to allow a better view of the monitor. As intubation is a dynamic process that requires the handle to move through a range of angles during the intubation attempt this means that at certain times during the attempt, the monitor will be at a less than ideal angle relative to the user (see FIG. 1).